The final year of this grant will involve a comparison of amalgams, composites and silicates that were placed under controlled conditions. As many patients as possible will be recalled and the restorations evaluated for marginal integrity, recurrent decay, corrosion and color stability. In a concurrent and more recent study, amalgam restorations were inserted next to previously placed inlays, then the sequence of placement was reversed. These patients will also be recalled and the changes recorded. All patients will be evaluated using Ryge criteria supplemented with 6X magnification color photographs. All clinically unacceptable restorations will be replaced and those removed will be analyzed with x-ray diffractions and electron probe in an attempt to evaluate any differences in corrosion products. All patients will be given an extensive dietary survey and these results analyzed by computer to determine if any correlation between diet and corrosion/staining can be established. Finally, a series of laboratory experiments involving impression materials, amalgams, handpieces and other biomaterials will be continued.